Welding Torch

DrPablo wrote in post #2363813
About 99% of UV rays are blocked by the coatings on your lens elements. If you're using an SLR, i.e. what your eye sees is what the lens sees, then there is no risk of UV rays passing through the lens, bouncing off the reflex mirror, and hitting your retina in any meaningful amount. The brightness alone, however, can damage your retina irrespective of UV transmission.

Incidentally, there is a reason why on CSI they use Nikons to take pictures of crime scenes. The reason is that Nikon (but not Canon) makes an SLR lens that transmits UV rays, which is useful for forensic pathologists to take pictures of subcutaneous bruising. This lens can do some amazing things when used with a filter that transmits UV but blocks visible light (i.e. the exact opposite of the typical UV filter)... see this gallery: http://www.naturfotogr​af.com/uvstart.html.

Unfortunately the lens costs $3000 -- otherwise I'd gladly adapt one to my own camera.

And Fuji which use Nikon lenses just released S3UVID body for forensic science.

You can always use an autodarkening shield to look thru the VF. I personally use the autodarkening shield when I weld. For the short period of time that I weld and the infequent times that I weld it comes in handy. Espencially important for those who don't weld autodarkening will definitely help save your eyes when unexpectantly the welder strikes an arc.

All lenses are not created equal nor are all coatings. Relying on the assumption that your lens has a coating which will block UV, I think, is dangerous.

Different coatings will block differing wavelengths of UV. The coatings on most lenses do block UV but are meant for the relatively small amount of UV light that is scattered about at sea level. This is to prevent your pictures from appearing "cold" i.e. a blue colour cast to them.

Even filters specifically designed to block UV (350nm-400nm) do a widely varying job.

How well does the retina heal after being burned?

I think what the Doc is prescribing is base on the fact that the uv ray will pass thru several layers of glass and reflected by a semi transparent mirror onto a prism/mirror to another mirror and then thru glass will greatly reduce the amount of uv to your eyes.

MagentaJoe wrote in post #2364160
All lenses are not created equal nor are all coatings. Relying on the assumption that your lens has a coating which will block UV, I think, is dangerous.

Different coatings will block differing wavelengths of UV. The coatings on most lenses do block UV but are meant for the relatively small amount of UV light that is scattered about at sea level. This is to prevent your pictures from appearing "cold" i.e. a blue colour cast to them.

Even filters specifically designed to block UV (350nm-400nm) do a widely varying job.

How well does the retina heal after being burned?

Point taken. I'm not an ophthalmologist, so I won't pretend to be an authority on this. But to the extent I know the subject, retinal burns are not caused by UV rays, but rather intense visible light. UV light and other forms of high energy radiation are mainly associated with cataracts.

I wasn't encouraging people to look at welding torches through their lens. Just saying that the rationale not to is not UV transmission, but rather the brightness intensity.

Whatever way you want to look at it, without being certain you have proper protection, it is foolhardy to look at a welding arc through the viewfinder.

I have suffered arc eye before and don't want anyone to go through that, it is terrible.

I was told by my family doctor many years ago, that the welder's flash I was experiencing was because my retina had been burned by the UV in the welders arc. Either he was wrong or I heard him incorrectly! Every reputable source I can find says something along these lines...

"Definition of Photokeratitis

Photokeratitis: A burn of the cornea (the clear front surface of the eye) by ultraviolet B rays (UVB). Also called radiation keratitis or snowblindness.

The condition typically occurs at high altitudes on highly reflective snow fields or, less often, with a solar eclipse. Artificial sources of UVB can also cause snowblindness. These sources include suntanning beds, a welder's arc (flash burn, welder's flash, or arc eye), carbon arcs, photographic flood lamps, lightning, electric sparks, and halogen desk lamps.

Symptoms include tearing, pain, redness, swollen eyelids, headache, a gritty feeling in the eyes, halos around lights, hazy vision, and temporary loss of vision. These symptoms may not appear until 6-12 hours after the UBV exposure.

Treatment consists mainly of keeping the eye closed with patches, after instilling a few drops of ophthalmic antibiotic solution, such as sulfacetamide sodium 10% with methylcellulose or gentamicin. Vision usually returns after 18 hours. The surface of the cornea usually regenerates in 24 to 48 hours.

Prevention involves sunglasses with adequate UVB protection and full coverage of the eyes (side shields)."

and another source...

"NTENSE VISIBLE LIGHT
Exposure of the human eye to intense visible light can produce adaptation, pupillary reflex, and shading of the eyes. Such actions are protective mechanisms to prevent excessive light from being focused on the retina. In the arc welding process, eye exposure to intense visible light is prevented for the most part by the welder's helmet. However, some individuals have
sustained retinal damage due to careless "viewing" of the arc. At no time should the arc be observed without eye protection"

So it appears that CORNEAL damage is from UVB and RETINAL damage is from VISIBLE.

I have seen this same question come up a number of times but only this time have I spent some time researching the actual facts beyond what I thought I knew.

MagentaJoe wrote in post #2364939
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So it appears that CORNEAL damage is from UVB and RETINAL damage is from VISIBLE.

I have seen this same question come up a number of times but only this time have I spent some time researching the actual facts beyond what I thought I knew.

UVB can cause lens damage as well (cataracts), which of course is behind the cornea. The cornea, being where it is, is exposed to all the particulates from welding as well.

i was doing some unmasked welding one day, at night bright lights were looking blury to me and out of focus. when i woke up i could barely see. some type of temporary cataracts. really freaked me out. took a day before I was seeing right.

morale: wear eye protection!

Ah you're one of those that do the turn head method of welding...

Yeah one of my manager tried to demonstrate that method to me but I just turn around and walk out while was demoing. He walked out of the welding shop like a blind mice.

I would have walked out too .Your eye site is precious and some risk it to try to get some pics of sun too.